Learnt something new today, if you need to shoot at a high ISO then overexpose the image by some amount +0.7 or +1.3 types, then run a noise reduction on this followed by correcting the exposure. That will give you usable images even at high ISO. Am posting the raw of a shot at 26000 ISO. Not as overexposed as I'd like but still a bit. See if this can be made into a better image
Raw link *www.dropbox.com/s/ea2bnan9ntf5vs8/DSC03983.ARW
My really bad attempt at this
*i.imgur.com/bLEn5az.jpg